Turbine rotor cooling



Nov. 8, 1949 G. K. W BOESTAD ET AL TURBINE ROTOR COOLING Filed Dec. l,1943 4 Sheets-Sheet l Nov. 8, 1949 G. K. w. BoEsTAD ET AL 2,487,514

TURBINE ROTOR COOLING 4 Sheets-Sheet 2 Filed Dec. l, 1943 5y IW`ATTORNEY G. K. W. BOESTAD ET vAl..

Nov. s, 1ga49 TURBINE ROTOR COOLING 4 sheds-sheet s Filed Dec. 1, 1943Patented Nov. 8, 1949 2,481,514 TURBINE no'ron oooLTNG Gustav KarlWilliam Boestad and hErik Otto Eriksson, Ldingo, Sweden, assignors, bymesno assignments, to Jarvis C. Marble, Leslie M. Me!- rill, and PercyH. Batten, as trustees Application December 1, 1943, Serial No. 512,474In Sweden January 16, 1943 6 claims. (ci. en -41) This application is acontinuation-in-part and as to common subject matter disclosedconstitutes a division of our copending application Serial No. 509,800filed November 10, 1943, (now Patent No. 2,462,600).

In turbines operating with high temperature motive fluid such forexample as in gas turbines, it is desirable to cool the turbine bl desparticularly the rotating blades, but it is diilicult and requires muchenergy to directly cool the rotating blades effectively, since theirtotal surface area. is large and the coefficients of heat transferbetween the gaseous motive fluid and the blade surfaces are very high.

1t is therefore a general object of the present invention to provideimproved rotor cooling means, more particularly for turbines of themulti-stage type, which will have a high cooling eiect and which willrequire only a small consumption of energy. stantially by the fact thatthe interior of vthe rotor communicates through channels with thepassage containing the blades, preferably with the space behind thefirst guide blade, so that the gaseous or vaporous cooling medium afterhaving passed the rotor escapes to said passage. According to a furtherfeature of the invention, the cooling agent has, immediately beforeentering the rotor, a pressure which is somewhat higher than thepressure of the driving medium in that portion of the passage whereinsaid channels open. In the application of the invention in gas turbineplants, the interior of the rotor communicates with a compressor or someother part of the gas turbine plant through conduits adapted to take offa portion of the working medium and to introduce the same into .therotor.

For example, if 3% of the air quantity delivered by the compressor isused for the cooling of the rotor and such air is introduced behind therst guide blade in a turbine comprising ten rotational blade rims, theloss in work for .the gas turbine plant will only be about 0.3%. Areduction of the temperature by` 100 C., permitting an increase of thetemperature of the driving or working medium by a corresponding amount,results in an increase of the quantity of heat utilized in the turbineof the magnitude of By the fact that the cooling medium is subjected topressure, the coelilcient of heat transfer between the same and thesurfaces of the rotor will be high.

If the rotor is composed of disks carrying the various rotational bladerims, which are provided with mutual radial spaces, and which areconnected with each other radially inside and outside these spaces, thelatter may communicate with one another through openings in the disks,said openings being located alternately on different radii. The air willthus have imparted thereto, simultaneously with the axial movement, arotary movement relatively to the rotor disks, whichA further increasesthe coecient of heat transfer between the cooling air and the walls ofthe rotor disks. It is important, moreover, that the outer por-tions ofthe rotor be cooled as effectively as that the path of heat conductionbetween the root of the blade and consequently the cooled rotor surfacebe short. By such construction .the blade root and the portion of theblade adjacent to the root and subjected to the highest stresses willalso be effectively cooled.

If there are no radial spaces as stated vabove in the rotor, which isthe case, for instance, where the rotor has an integral blade-carryingpart, the cooling channels are arranged outside ,the average diameter ofthe rotor and preferably near the peripheral portion of the rotor, toensure effective cooling of the blade attachments, besides which thewhole rotor is kept at a low temperature inside the channels.

Further objects and advantages of the invention will be apparent fromthe following description considered in connection `with theaccompanying drawings which form a part of this specication, and ofwhich:

Fig. 1 is a horizontal view, partly in section, of a gas turbineconstructed in accordance with the invention.

Fig. 2 shows the portion of the turbine framed by the lines'-Z-Z-Z inFig. 1, on an enlarged scale.

Fig. 3 shows a gas turbine according to another embodiment and in thesame projection as in Fig. 1.

Figs. 4 and 5 show two embodiments of gas turbine plants, partly insection, said plants being provided with a cooling device in accordancewith the invention. Y

In the various ngures, corresponding parts have been designated by thesame reference numerals.

In Fig. 1, I designates the rotor generally which is composed of anumber of turbine disks I2, the inner diameter of which is spaced apartfrom the axis of rotation, so that an inner axial passage I 4 isproduced. The disks I2 are preferably connected with each other throughwelding both at the inner and at the outer peripheral portions thereof,as indicated at I6, I8 (Fig. 2). The spaces 20 provided between theturbine disks and extending nearly out to the blade attachments willthus become sealed against the surrounding. The turbine disks I2 areprovided with axial channels 22 which are disposed alternately ondiierent radii and connect the various spaces 20 with eachother.

'I'he disks I2 of the rotor carry blades 24 which are arranged, togetherwith guide blades 26 secured in the turbine housing 8, in a passage 3Uhaving the gaseous working medium -owing therethrough. The outermostturbine disk I2 on the left hand side in Fig. 1 (the high pressure sideof the turbine) may, over a preferably conical portion 32, be madeintegral with a shaft 34 cooperating in known manner with radial andaxial thrust bearings 35 secured in the turbine housing. Arrangedbetween the portion 32 and the shaft 34 are packing members 36, 38 onboth sides of the bearing 35. The outermost disk I2 on the opposite sideof the rotor is connected to a shaft 44 mounted in bearing 42. A smallportion of the working medium of the gas turbine plant, such as the airwhich is compressed by a compressor contained in the gas turbine plant,may be conveyed through a socket 46 to an annular chamber 48 in thehousing 28 and thence through channels 50 as well as through channels 5I-inthe iirst guide blade i'im 26 at the high Pressure end of the turbineto channels 52 opening into a chamber 54 at the left hand of the disk I2in the drawings. From the chamber 54, the cooling air iiows through 'thechannels 22 to the spaces 20 in the rotor, a relative rotary movementbeing set up between the cooling air and the Vwalls of the turbine disk,so that high coeiicients of heat transfer are obtained. The cooling airthen` enters the channel I4, which is closed on both sides, andcontinues through a radial channel 56 in the rst turbine disk I2 at thehigh pressure end of the rotor, whereupon the cooling air is introducedinto the space 58 behind the rst guide blade 26 and is carried alongwith the current of driving medium iowing through the passage 30. Thespace 58 is separated from the chamber 54 by means of packings 60.

The cooling air is taken off at such a point on or behind the compressorvthat when entering the interior of the rotor it will have a pressureomewhat higher than the pressure in the space The rotor I0 may be madefrom steel of the martensitic or some equivalent type. On the otherhand, the blades 24 are made from itic or some equi alent steel having ahigh heat resistivity. The latter steel at the same time hasacoeiiicient of heat expansion about 50% greater and a less heatconductivity than martensitic steels. Hereby, the rotor proper as Wellreduced to a great extent. comparatively small portion in temperatureare The blades occupy a greater heat of the blades is of littleexpansion on the part import. The turbine Furthermore, the housingagainst the hot working 28 may be protected medium by means of thepoints of attachment o1' the blades 24 as possible. The channels 62 areno through-pas sages at the right hand end of the rotor I 0 in thedrawing, but communicate through radial channels 64 with the centralchannel I4. The cooling air is conveyed from the space 48 to the chamber54 through passages 66, 68 in reinforcing members 'I0 located in frontof the first guide blade and in the housing 28.

The gas turbine plant illustrated in Fig. 4 comprises a compressor 12which is driven by the gas turbine 14, the blade-carrying rotor I D ofwhich may form an integral part as in the embodiment according to Fig.3. The air comthrough the channels 62, I4, 56 to the rear side of therst guide blade rim 26 in the A conduit 90 extending from the conduit I6may be connected with the a three-way valve 93 being inrotor in normaloperation.

It is advantageous to form the turbine in such essieu manner that-therotor may bel heated up` more in normal operation of the turbine. Toobviate disadvantages of this kind, there I Y valve 92 in the conduit 16behind the outtalefor the conduit 90, viewed in the direction of flowofthe air. The valve 92 is closed more or less, whil the fuel supply g atthe same time. All air from the compressor 96 now flows through conduits90, 9| to the interior of the rotor. To this end the valve 93 may beoperated automatically to open the passage between the said conduitswhen the valve 92 is closed. Through the kinetic energy of the rotatingmasses, the rotor is kept running for a while, and the rotation may bemaintained for a longer time with the aid of the starting motor 94, ifrequired. In this way, an efficient cooling of the rotor may be had alsowhen the rotation is slow.

In the embodiment according to Fig. 5, 12 designates a low pressurecompressor and 96 a high pressure compressor, the conduit between themhaving an air cooler 90 arranged therein. 14 denotes the low pressureturbine driving the compressor, and designates the high pressure turbinedriving the compressor 96. The air compressed in the compressor 96 toits final pressure flows through the conduit 16, the heat exchanger 00and the combustion chamber 84 to the gas turbine |00 and from the latterto a combustion chamber |02, into which the fuel is introduced through anozzle -|045 to reheat the working meenters the turbine 14. The turbine14 also drives a generator (not shown). for example. In both turbines,the rotor is provided with a system of cooling passages according to theinvention.

Extending from the conduit 82 and preferably also from the conduit 16are conduits |03 and |05, respectively, which by the three-way valve 93are connected to a conduit |06. Cooling air is supplied through saidconduits and a branch conduit |08 to the rotor of the high pressureturbine |00. The conduit |06 communicates with a conduit ||2 extendingfrom the outlet |0| of the high pressure turbine to the cooling systemof the low pressure turbine, as well as withV a conduit |01 opening intothe chamber 54 of the low pressure turbine. The conduit |01 may have acooler ||0 connected into the same. Provided between the conduits |06,|01 and H2 is a three-way valve |I4 adapted to cut oir the conduit |06.in normal operation, when cooling medium passes through the conduits||2, |01 and through the cooler I|0 to the low pressure turbine. Whenthe gas turbine plant is put out of operation, the valve H4 is shiftedsimultaneously with the closing of the valve 92, so that cooling airwill now pass through the conduits |06 and |01 to the low pressureturbine. The valve 93 then also takes a. position to allow a flow of airthrough the conduits and |06. By this means, powerful cooling of bothrotors will be obtained.

If desired, small holes or gaps may be provided in the outerbond of thedisks I2 in the embodiment according to Figs. 1 and 2, said holes orgaps opening into the passage for the driving medium, to which passage aportion of the cooling air will thus escape directly.

Gas turbine system structure herein disclosed slowly, vwhereby Y sionalapplicatie and the sealing edges btween the latter may be worn togreater plays 'A is' provided ef 'l0 1 e l through the nozzle 86 is outoff p tionary structures forms' the claimed subject se, and 'whileseveral embodiments it is to be underof the latter havebeenvshown,

- [steed that theyareiiuustreuveoniy and that the Y scope of theinvention includes all forms' of structure' falling'J-within "the'purview of' the appended Y what we claimvis: 1j i. 1'. In an elasticiuitiA turbine,

carrying rotating andstationary biadesfirespectively and providing'between them a channel having 'a blade'y system therein for expansionof motive 'fluid, the'interior. of said rotor being providedwith'passages for conducting a fluid cooling'medium therethrough to coollthe blade carrying structure ofthe rotor, inlet means for introducing acooling medium under pressure to said passages and outlet means fordischarging the cooling medium from said passages to said channel, saidoutlet means communicating with a zone in said channel on the dischargeside of at least the first row of blades in said blade system, andsealing 4means between said rotor and stationary structures located toclose communication between the inlet side of said first row of bladesand the place of communication of said outlet means with said channel.

2. A structure as set forth in claim 1 in which said cooling passagesare arranged so that the cooling medium iows from said inlet meansgenerally lengthwise of the rotor adjacent to the periphery of the bladecarrying portion of the rotor structure.

3. A structureas serl forth in claim 1 in which said cooling passagesare arranged so that the cooling fluid flows from the inlet theretogenerally lengthwise of the rotor adjacent to the outer periphery of theblade carrying portion of the rotor structure and thereafter owsgenerally lengthwise of the rotor through the central portion thereof.

4. A structure as set forth in claim l having said inlet means at thehigh pressure end of the rotor, said cooling passages comprisingpassages in the radially outer part of the blade carrying structure ofthe rotor communicating with said inlet means for flow of the coolingmedium generally lengthwise of the rotor in the outer part thereof and acentrally located passage communicating with the passages in saidradially outer part for return flow of cooling medium from the outlettoward the inlet end of the rotor, and said outlet means comprisingpassages for discharging the cooling medium from said central passage tothe motive fluid channel adjacent to the inlet end of the rotor.

5. A structure as set forth in claim-1 having a hollow integral rotorstructure, said cooling passages comprising a plurality of passagesextending lengthwise through said structure and communicating at thehigh pressure end of the rotor with said inlet means and a centralcooling passage communicating adjacent to the outlet end of therotor'with said lengthwise extending passages and Said outlet meanscomprising between said central passage and the channel for motivefluid.

6. A structure as set forth in claim 1 in which the blade carryingportion ofthe rotor comprises a plurality of discs connnected togetheradjacent to their outer peripheries and also at places mattter of ourdivi- Y Serial No.1'18,262 filed Febru- Aary 25, 1949, the claimedsubject matter -in the @present application lbeing restricted' toturbine structure per .rotor sta.-

spaced inwardly thereof, whereby to provide s, se-

ries of annular spaces between the discs, and openings in said discs forconnecting said spaces to provide therewith the cooling passagesaforesaid, said openings being so located relative to 5 each other inadjacent discs as to prevent straight axial ow through the rotor of thecooling medium and said spaces being connected for direct ow thereto ofthe cooling medium from said inlet means. f

GUSTAV KARL WILLIAM BOESTAD. ERIK OTTO ERIKSSON.

REFERENCES CITED The following references are of record in the 15 fileof this patent:

` 8 UNITED STATES PA'I'ENrs Number Number

